1. Field of the Invention
This invention relates to fluid pressure operated electrical switches, responsive to a predetermined range of pressure from a hydraulic system, or in any particular branch or part of said system.
2. Description of the Prior Art
It has been proposed in fluid pressure operated electrical switches to provide a piston element responsive to the fluid pressure to actuate the switch with a limitation of the stroke to a predetermined extent by employing a stopper member for the piston in front of the piston element for avoiding damage of the switch due to overstroking. Such arrangement is usually relatively complicated and installation is accordingly complicated. Further, the conventional switches have sealing means for sealing the piston element and which is normally exposed to operating fluid pressure. This tends to result to a short life span of the sealing means.
Still further, the conventional switches are provided with a spring to restore the piston element against the operating fluid pressure and an adjusting member to adjust the spring force of the spring in order to provide a proper responsiveness of the piston element to the operating pressure. Such adjusting member is customarily disposed outside the convenient reach of the operator.